The present invention relates to heating, ventilation and air conditioning (HVAC) duct systems and, more specifically, it relates to a folded and hinged plastic connector for use with HVAC duct work.
HVAC systems are designed to provide control of space temperature, humidity, air contamination, differential pressurization, and air motion. These distribution systems use a network of ducts to deliver the heated and/or cooled air to the various rooms and spaces within the building structure. These air ducts are usually rectangular or round passages and are made from a variety of materials. When these ducts are accurately sized and the duct system is correctly designed, the air will be delivered to the rooms and spaces with a minimum of resistance.
Of the many HVAC systems currently available, galvanized sheet steel duct systems are among the most widely used. These systems generally consist of an air heating and/or refrigeration unit, straight sections of duct, and multiple types of fabricated fittings and connections. From these fittings and connections, the straight sections of duct are connected to each other and to openings or vents in the rooms and spaces of the building structure. Currently, the duct and the connections and fittings are fabricated primarily by experienced sheet metal workers.
In recent times, several issues have developed with the design of the connections and fittings used in HVAC systems. First, the connections and fittings are difficult to store, handle, and transport without damaging them. In addition, due to their current shape and design, they require a large quantity of space per unit to store and transport. These problems cause excessive scrap and increased inventory holding and transportation costs for the distributor and customers.
In order to solve some of these problems, at least with duct-to-register connections, it has been proposed to fabricate sheet metal duct-to-register connectors which can be blanked and partly folded at the factory, shipped stacked compactly together, and bent into final form at the site of installation. Thus, in McGann U.S. Pat. No. 3,606,404 there is disclosed a sheet metal strip, foldable to a rectangular cross-section to fit within a register aperture, which has a margin along one of its longer edges to bend an inward shoulder, and bendable tabs extending therefrom. The shoulder seats against the outer margin of a duct opening smaller than the room surface aperture for the register. But, metal stamping of such parts requires expensive dies and equipment and the parts still must be finally formed at the site. Even then, the duct-to-register connectors of McGann are designed for use only with wood floor joists.
Another issue with the current design of the connections and fittings used in HVAC systems is the excess labor and materials cost that is often required when installing them into cement slab foundations. Without consulting all of the building codes and standards for all of the locations in which this product may be used, general installation practices demand that the duct must be painted and wrapped in plastic bags to prevent rust and corrosion when placed in a cement slab foundation. Accordingly, it would be desirable to have plastic duct work or at least plastic duct connectors.
Of course, in other fields plastic ducts are known. For example, Corsi et al in U.S. Pat. No. 4,942,271, discloses a plastic duct assembly for enclosing conduits, cables, wires, lines and the like, comprising a base having a generally U-shaped cross section along its longitudinal axis. The base includes a generally planar central portion with first and second legs extending substantially perpendicular thereto. The cover includes an intermediate portion having third and fourth legs extending substantially perpendicular thereto. The cover is pivotally and releasably coupled to the base at one end and releasably coupled to the base at the other end. The pivotal and releasable coupling is made up and released via a snap fit resulting from forces exerted substantially perpendicular to the longitudinal axes of the cover and the base. But, the Corsi et al plastic duct is not designed for use with HVAC systems. In addition, it cannot be stored and transported in the unfolded, flat position and cannot be stacked in that position to save space. It is, therefore, as awkward to handle as much of the prior art duct work.
Thus, most prior art fittings and connections are often very awkward to use and handle. The current design allows very little flexibility in assembly which in some cases increases labor and scrap cost. They also contain sharp edges and corners which occasionally cause cuts and abrasions which increase labor cost and put the laborers' safety at an unneeded risk.
Accordingly, the need still exists for inexpensive devices that provide ease of assembly and opportunities for cost reduction in labor, scrap, and inventory holding costs currently associated with HVAC duct systems.